A data processing environment comprises a variety of hardware, software, and firmware networking components. A physical network, also called an underlay, is a network defined using such components. Techniques are available presently to construct a logical network, also known as a software defined network (SDN) overlay (hereinafter “overlay,” “overlay network,” “overlay virtual network,” or “OVN”) from such networking components. Essentially, networking components are abstracted into corresponding logical or virtual representations, and the abstractions are used to define the overlay. In other words, an overlay is a logical network formed and operated using logical representations of underlying networking components. An overlay virtual network includes nodes and logical links that are built on top of an existing network for the purpose of implementing and providing a network service that is not available in the existing network.
A hypervisor, also referred to as a virtual machine monitor (VMM), is a piece of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor is executing one or more virtual machines is defined as a host machine. Each virtual machine is called a guest machine. The hypervisor presents guest operating systems with a virtual operating platform and manages the execution of the guest operating systems. Multiple instances of a variety of operating systems may share the virtualized hardware resources.
A virtual machine (VM) comprises virtualized representations of real hardware, software, and firmware components available in a data processing system. The data processing system can have any number of VMs configured thereon, and utilizing any number of virtualized components therein. The data processing system is also referred to as a computing node, a compute node, a node, or a host.
A virtual switch, sometimes herein referred to as a vSwitch, is a software application that allows communication between VMs. A virtual switch is completely virtual and can connect to a network interface card (NIC). A virtual switch merges physical switches into a single logical switch. This helps to increase bandwidth and create an active mesh between servers and switches. A virtual switch may be embedded into a server's installed software or included in a server's hardware as part of its firmware.
In large scale data processing environments, such as in a data center, thousands of VMs can be operating on a host at any given time, and hundreds if not thousands of such hosts may be operational in the data center at the time. A virtualized data processing environment such as the described data center is often referred to as a “cloud” that provides computing resources and computing services to several clients on an as-needed basis.
Network virtualization by defining overlay networks is an emerging trend in the management and operation of data centers and cloud computing environments. One of the goals of network virtualization is to simplify the network provisioning in multi-tenant data processing environments, as well as dedicated customer data processing environments.
Unicasting is a method of sending data point-to-point, to wit, from a single sender to a single receiver. Broadcasting is a method of sending the same data to all possible destinations. Another multi-destination distribution method, multicasting, sends the same data only to interested destinations called receivers by using special address assignments. Internet Protocol (IP) multicast is the process of multicasting IP packets to several receivers in a single transmission of the IP packet. IP multicast is a popular technique used to help conserve bandwidth in the data center and reduce the load on servers.
IP multicast operating in an overlay network is called overlay multicast. Overlay multicast can be achieved in different ways, depending on the support for multicasting provided in the underlay network. Multicast based overlay multicast requires the underlay network to provide support for multicasting. Multicasting in underlay networks is not presently prevalent in data processing environments. Multi-unicast based overlay multicast is a method to transmit multicast packets in the overlay network where the underlay supports unicasting but does not support multicasting.